Subterranean formation operations (e.g., stimulation operations, sand control operations, completion operations, and the like) often involve placing a cement column around a casing or liner string in a wellbore. The cement column is formed by pumping a cement slurry downhole through the casing and upwards through the annular space between the outer casing wall and the formation face of the wellbore. After placement, the cement slurry develops into a gel and then cures in the annular space, thereby forming a column of hardened cement that, inter alia, supports and positions the casing in the wellbore and bonds the exterior surface of the casing to the subterranean formation. Among other things, the cement column may keep fresh water zones from becoming contaminated with produced fluids from within the wellbore. As used herein, the term “fluid” refers to liquid phase and gas phase materials. The cement column may also prevent unstable formations from caving in, thereby reducing the chance of a casing collapse or a stuck drill pipe. Finally, the cement column forms a solid barrier to prevent fluid loss to the formation, contamination of production zones, or undesirable fluid invasion into the well. Therefore, the degree of success of a subterranean formation operation depends, at least in part, upon the successful cementing of the wellbore casing.
The control of fluid losses to the formation is important in cementing and other types of downhole operations such as drilling and fracturing. If fluid losses occur in an uncontrolled manner, many problems may happen. For example, filtrate invasion from a cement column into production zones may cause formation damage, which may reduce the production potential of a reservoir. In cementing, fluid losses above a safe threshold can lead to failure of the operation, which may require expensive remedial cementing operations. In the worst cases, fluid losses may lead to gas invasion and migration, which can lead to the blow-out of the well.
The current recommended procedures to measure fluid loss data use a filter screen to simulate the formation permeability. By fixing the formation permeability, successive tests of different slurry designs with and without fluid-loss-control additives provide a comparison between cement slurries. As a result, designs that minimize filtration losses in specific conditions simulated in a laboratory can be obtained. However, this comparison provides only a relative measure between different cement slurry designs. For example, two cement slurries A and B can be tested and it can be found, for example, that slurry A has a smaller filtration loss than slurry B. However, the filtrate volume loss measured in laboratory conditions following the current recommended procedures cannot be used as an input to a mathematical model representing the physics of the filtrate loss. Consequently, this laboratory measurement cannot be used to predict the filtrate loss observed in the field. Therefore, it is desirable to measure the physical properties of the fluid of interest related to the filtration phenomenon.